# Coding Conventions (Repository-Specific)

## Language and Style

- Default to JavaScript for new work unless area is already TypeScript.
- Use existing formatting:
    - 4 spaces
    - no trailing commas
    - preserve existing quote style in touched file
- Avoid broad stylistic rewrites in functional changes.

## File Placement and Boundaries

- Keep `pages/` focused on route wiring, data fetch orchestration, and composition.
- Move reusable domain logic into `lib/` or `actions/`.
- Keep reusable UI in `components/` (feature subfolders preferred).
- Keep Redux behavior changes localized to relevant slice and `store/store.js` integration points.

## API Route Conventions

- Follow existing API naming where present (`*_api.js` in `pages/api/endpoint`, `pages/api/file`, `pages/api/admin`).
- Maintain explicit error handling and return predictable response shapes.
- For sensitive endpoints, include authorization and invalid-input paths.

## Auth/Session Conventions

- `pages/api/auth/[...nextauth].js` is authoritative for auth flow behavior.
- Do not bypass session checks in protected routes/components.
- Preserve secure redirect/callback behavior and cookie safety settings.

## i18n Conventions

- Add user-facing strings to locale files (`locales/en`, `locales/cy`) where feasible.
- Keep EN/CY route behavior aligned when adding/changing pages.
- If a route alias changes in Welsh, verify rewrite mapping in `next.config.js` and page namespaces in `i18n.js`.

## Accessibility Conventions

- Use semantic HTML and maintain heading hierarchy.
- Ensure keyboard access and visible focus states.
- Provide meaningful labels and error messages.

## Logging and Error Handling

- Never log secrets, tokens, personal details, or raw credential payloads.
- Keep operational logs concise and safe for production telemetry.
- Prefer structured, actionable errors over generic catch-and-ignore patterns.

## Legacy and Mixed-Pattern Guidance

- Where conventions conflict between folders, follow the dominant local pattern and record exceptions in `memory-bank/decisions.md`.
- Refactor incrementally: separate behavior changes from structural cleanup.